package com.thealgorithms.dynamicprogramming;

/**
 * The {@code Tribonacci} class provides a method to compute the n-th number in the Tribonacci sequence.
 * N-th Tribonacci Number - https://leetcode.com/problems/n-th-tribonacci-number/description/
 */
public class Tribonacci {

    /**
     * Computes the n-th Tribonacci number.
     *
     * @param n the index of the Tribonacci number to compute
     * @return the n-th Tribonacci number
     */
    public static int compute(int n) {
        if (n == 0) return 0;
        if (n == 1 || n == 2) return 1;

        int first = 0, second = 1, third = 1;

        for (int i = 3; i <= n; i++) {
            int next = first + second + third;
            first = second;
            second = third;
            third = next;
        }

        return third;
    }
}
